EM/IA

I have followed, and perhaps mildly stalked, EM/IA’s work for years, and lately I had been thinking seriously about trying one of their Remote Autoformers. Buying one new at full price would, however, have made for a fairly expensive experiment if it did not work out in my system. Then, while casually perusing Trade Me, I spotted an earlier Manual version for sale, so I snapped it up. The seller turned out to be one of my own clients, and he even hand-delivered it to me at work. Acquiring it this way allows me to explore the autoformer approach at a significantly lower cost and discover whether it is a path I might want to follow further. This of course is born of my obsession with the idea of getting a Komuro 300B power amp for my O/Bronzes…
The uniquely individual approach of the EM/IA chaps to audio, particularly their use of transformers, magnetic components and deceptively simple circuits, has fascinated me. Until now, however, I have never had the opportunity to dabble in any of it myself. That has finally changed with the arrival of this Manual Autoformer, its a small and intriguing box that takes me into a totally new corner of audio. It’s an unusually compact passive line controller that embodies a very different approach to controlling volume. At only around 140mm in each dimension, it is physically discreet, although there is enough mass in the little chassis to keep it planted on the shelf. It even arrives in its own hard case, perhaps unnecessary, but undeniably cool.

EM/IA brings together Jeffrey Jackson’s Experience Music and Dave Slagle’s Intact Audio. It is less a conventional audio manufacturer than a collaboration between two highly individual designers, combining Jackson’s experience with complete components and systems with Slagle’s deep knowledge of transformers, magnetic materials and winding techniques. The name itself is drawn from Experience Music and Intact Audio. Their products are handmade, understated in appearance and very much centred on the idea that the important jewellery belongs inside the box. EM/IA describes the partnership as the result of more than fifty years of experimentation and listening.

I had, of course, heard of using autoformers for volume control, but it was one of those corners of audio that I had never explored. The basic idea is quite different from the conventional resistive potentiometer found in most preamplifiers. Instead of lowering the signal by dissipating part of it through resistors, an autoformer uses a single tapped winding. Selecting different taps changes the relationship between voltage and current, like changing gears. As the voltage is reduced, more current becomes available, helping preserve drive into the following amplifier. There is no active gain stage, no power supply in the signal path and remarkably little between the source and amplifier beyond wire, magnetic core material and the switching arrangement.

This unit is fully dual mono and provides attenuation from 0 to –52.5dB in 2.5dB steps. Two inputs and parallel outputs adorn the back, making the seemingly simple little cube more flexible than it initially appears. The case itself is nicely damped with some deadening material.

The centre knob provides what is effectively a penalty-free balance adjustment of 1.25dB or 2.5dB to either the left or right, without inserting a conventional balance potentiometer into the signal path. If a greater correction is required, the dual-mono operation allows each channel to be adjusted independently, making virtually any desired offset possible in 1.25dB increments. It is an elegant solution, particularly for slightly asymmetrical rooms, recordings with imperfect channel balance or cartridges that do not produce precisely equal output from both channels.

Until now, I have only ever used active preamplifiers, so the EM/IA represents a genuine departure from my usual approach. I have never previously explored what a properly implemented passive design might offer, and I am curious to discover whether its apparent simplicity can provide something musically compelling without sacrificing drive, weight or dynamics. The EM/IA is a beautifully focused piece of engineering: compact, deceptively simple and designed to control volume while interfering with the signal as little as possible. Having known about this approach without ever seriously investigating it, I am very interested to hear how it settles into the system and whether this unassuming little cube can make a persuasive case for removing the active line stage altogether.  Much of the reputation surrounding the EM/IA centres on its transparency, the sense that it imposes remarkably little of itself on the signal. That is particularly interesting to me, as transparency is one of those qualities frequently claimed but not always convincingly demonstrated. It will be fascinating to hear the autoformer in action and discover whether its minimalist approach really does allow more of the source, recording and associated equipment to come through unaltered.

Initially, I am borrowing an Audio Note UK P3 300B SET power amplifier to use with it for a few days, purely as an experiment and a chance to explore what this sort of setup can do. I am curious to discover whether the apparent simplicity of a properly implemented passive design can provide something musically compelling without sacrificing drive and weight or dynamics.

Experiments continue…